A vehicle body reinforcement device that may be attached on a vehicle and that is supported on a vehicle body via brackets that are disposed at opposing ends of the vehicle body in an axial direction is known. For example, as disclosed in JP4865698B (hereinafter referred to as Patent reference 1), a reinforcement device for a vehicle body is specified by various requirements in order to provide the reinforcement device for the vehicle body of the vehicle that easily enhances a riding comfort by selective attachment and removal of the reinforcement device for the vehicle body in accordance with a preference of a driver (see Paragraph [0011] of Patent reference 1). The reinforcement device for the vehicle body of a vehicle is formed in an elongated shape and includes an oil-pressure-type damper that is provided on an intermediate portion of the reinforcement device for the vehicle. The oil-pressure-type damper serves as an oil-pressure-type damping force generating device that generates damping force against a deformation of the reinforcement device for the vehicle body expanding and contracting in a longitudinal direction of the reinforcement device for the vehicle body (see Paragraph [0012] of Patent reference 1).
A known vehicle body reinforcement unit is disclosed in JP2015-3546A (hereinafter referred to as Patent reference 2). The vehicle body reinforcement unit includes a reinforcement member and a displacement inhibition mechanism. The reinforcement member is disposed between a pair of frame portions of a vehicle body. The displacement inhibition mechanism applies biasing force against a displacement of the pair of frame portions, the displacement that corresponds to at least one of enlarging displacement of the pair of frame portions in a direction enlarging a relative distance between the pair of frame portions, and contracting displacement of the pair of frame portions in a direction contracting the relative distance between the pair of frame portions (see Paragraph [0011] of Patent reference 2). Similarly, a vehicle body reinforcement unit is disclosed in JP2015-3547A (hereinafter referred to as Patent reference 3). The vehicle body reinforcement unit disclosed in Patent reference 3 includes a pair of displacement members and a damper mechanism. The pair of displacement members is relatively displaced in response to a relative displacement of a pair of frame portions. The damper mechanism applies braking force to the pair of displacement members that moves relatively. As disclosed in Patent reference 3, the damper mechanism may include a cylindrical portion, an internal fitting portion, a friction member, and a biasing member. The cylindrical portion serving as one of the pair of displacement members is coaxial with an axis of a reinforcement member in a longitudinal direction of the reinforcement member. The internal fitting portion serving as the other of the pair of displacement members is coaxial with the axis of the reinforcement member and internally fits in the cylindrical portion. The friction member is in contact with an inner circumference of the cylindrical portion or an outer circumference of the internal fitting portion. The biasing member biases the friction member in a contact direction where the biasing member and the friction member come in contact with each other (see Paragraph [0011] and [0013] of Patent reference 3).
The reinforcement device for the vehicle body disclosed in Patent reference 1 includes the oil-pressure-type damper as a damping force generation device. However, not only that the damping force against the displacement of the reinforcement device for the vehicle body is not easily adjusted, but also that various oil-pressure-type dampers are required in accordance with a type of a vehicle or a portion on which the damper is mounted. Accordingly, the reinforcement device for the vehicle body disclosed in Patent reference 1 lacks versatility in terms of a retrofit that is mountable on the vehicle. On the other hand, each of the vehicle body reinforcement units disclosed in Patent references 2 and 3 has the versatility. The structure is easily established and the cost may be reduced (see Paragraph [0012] of Patent references 2 and 3). However, the upsizing of the vehicle body reinforcement units disclosed in Patent references 2 and 3 is inevitable, and further modification is desired. Specifically, the displacement inhibition mechanism and the damper mechanism disclosed in Patent references 2 and 3 are desired to include structures in which appropriate pressure load may be applied without upsizing the devices.
A need thus exists for a vehicle reinforcement device which is not susceptible to the drawback mentioned above.